Flowering phenology of myrtaceous trees and their relation to climatic, environmental and disturbance variables in northern New South Wales

Patterns of flowering phenology, which represent a partial description of f ood availability for nectarivores, are described for 20 species of myrtaceo us trees on the mid-north coast of New South Wales (NSW), Australia. Data w ere recorded monthly between 1982 and 1992 across 23 sites that comprise a variety of local environmental conditions and disturbance histories. Flower ing periodicity and intensity were highly variable between species and site s, ranging from annual flowering to no flowering over the 10-year period. C ool temperatures prior to floral budding was a strong predictor of flowerin g for nine species. Extraordinary climatic events also influenced flowering . The period of greatest flowering for all species combined occurred 9 mont hs after the highest monthly rainfall recorded in the survey (March 1985). An 18-month extreme drought led to poor flowering in Corymbia variegata, Eu calyptus acmenoides, Eucalyptus grandis and Eucalyptus resinifera, but reco very after the drought broke was rapid. In contrast to climate, few site-ba sed environmental variables explained the intersite variation in flowering performance of the tree species. Site disturbance from logging at two sites during the survey did not influence flowering in the remaining canopy over following years. No species showed a negative correlation with a history o f recent logging, and direct comparisons, between large- and medium-sized t rees, of the percentage of foliage in flower showed no differences for any species. At the scale of a timber production forest, the negligible effect of tree size (if > 10 cm diameter at breast height over bark), and high ste m density resulting from selective logging, leave about half of the net har vestable area producing flowers at a similar density to unlogged forest. Ho wever, larger trees flowered more frequently than medium-sized trees in C. variegata (medium: every 5.9 years; large: every 2.3 years) and there was a trend in this direction for 13 of 17 species. Low-intensity burns and wild fires caused differing amounts of crown scorch, sometimes resulting in bud loss, but most species flowered at prefire levels 1-3 years after the distu rbance. Eucalyptus microcorys and Angophora costata flowered poorly at site s that experienced frequent low-intensity burns. Regionally, blossom shorta ges occur through a combination of spatial and temporal patchiness in flowe ring and the clearing of those species that occurred on soils preferred for agriculture. On the north coast of NSW, these shortages commonly occur fro m late winter to spring. Species that flower reliably in this period includ e Eucalyptus robusta, Eucalyptus tereticornis and Eucalyptus siderophloia i n late winter and E. siderophloia and E. acmenoides in spring.